At the bottom of the dildo there is often a wider base in the form of a suction cup or realistic scrotum which means they fit most harnesses. The wide base means that the dildo sits firmly in place without going through the hole or the so-called O-ring on the harness.

There are also strapon dildos with a hole in the bottom that allows you to easily attach them to your Vac-U-Lock-Harness.

If your strap-on dildo has a suction cup, it is just as wonderful to use separately. You can attach it to flat surfaces in the home to enjoy from different positions and angles while keeping your hands free for other things.